Channels in a communication network may typically experience channel distortion. This channel distortion may result in intersymbol interference (ISI), which essentially is the spreading of a signal pulse outside its allocated time interval causing interference with adjacent pulses. If a communication channel is uncompensated with respect to its intersymbol interference, high error rates may result. Various methods and designs are used for compensating or reducing intersymbol interference in a signal received from a communication channel. The compensators for such intersymbol interference are known as equalizers. Various equalization methods include maximum-likelihood (ML) sequence detection, linear filters with adjustable coefficients, and decision-feedback equalization (DFE).
Linear and DFE equalizers at the receiver end of a communication system are generally accompanied with increased noise characteristics. The increased noise characteristics may be reduced with an equalizer placed at the transmitter end. Such a design relies on the channel response being a known factor to the transmitter. Since channel characteristics may vary with time, design of the complete equalizer at the transmitter end is not straight forward. However, the channel characteristics do not vary significantly over time in wire line channels. This lack of time variation allows for a DFE feedback filter to be placed at the transmitter and a DFE feedforward filter at the receiver. However, using such a DFE design may result in the signal points at the transmitter, after subtracting intersymbol interference, having a larger dynamic range than the original set of signals, thus requiring larger transmitter power. The problems associated with increased required power may be addressed with precoding information symbols prior to transmission. However, to provide higher speed reliable data communication what is needed are enhanced schemes for providing channel equalization, which at the same time can be implemented without a significant amount of complexity.